Method, device and software for separating the individual subjects of an anatomical structure segmented from 3d datasets of medical examination procedures

ABSTRACT

The invention relates to a method for carrying out the imaging processing of data sets of three-dimensional characters obtained from medical examination methods. According to the invention, a separation of the data of relevant anatomic structures as well as of other structures is carried out based on data provided in the form of volume elements. In addition, a spatial representation of at least one structure of interest ensues, and the individual objects of the structure of interest are separated from one another in such a manner that enables them to be repositioned in the spatial representation.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention is directed to a method, a device and a softwareproduct for the medical image processing of datasets of athree-dimensional character acquired from medical examinationprocedures, of the type wherein a separation of the data of relevantanatomical structures as well as of other structures is undertakenproceeding from data in the form of volume element, and a spatialpresentation of at least one structure of interest ensues.

[0003] 2. Description of the Prior Art

[0004] The human ability to conceptualize quickly reaches it limits inthe spatial interpretation of the information from X-ray exposures orfrom tomograms as acquired with modern tomographic methods. Modernmethods of medical image processing therefore convert the information ofa three-dimensional character acquired in medical examinations intospatial impressions of the inside of the body. In general, however, itis not adequate to merely convey a spatial impression of the displayedbody region to the medical practitioner. For preparing a reliablediagnosis or for planning a therapeutic measure or a surgicalintervention, however, the medical practitioner needs a reduction of thedisplayed data to what is essential to the practitioner. In other words,the subject of the practitioner's interest must clearly contrast withthe environment having only secondary informational content. A number ofmethods were developed for this purpose that enable an allocation ofindividual measure values to relevant anatomical structures such as, forexample, nerves or fat tissue, bones or tissue equivalent to muscle, aswell as to non-anatomical structures such as, for example, foreignbodies. These methods are referred to as segmenting and form thepre-condition allowing a medical practitioner to view, for example, thebone structure of a patient at the picture screen isolated from othertissues.

[0005] For planning a surgical intervention, for example after anaccident resulting in a complicated fracture, however, this form ofpresentation of the examination results is often inadequate sincealthough it reflects the actual condition of the structure of interestit does not allow a manipulation of the data with respect to measures tobe undertaken; the individual subjects within each and every structureremain fixed in their geometrical arrangement relative to one another inknown segmenting methods. The preparation for an intervention to treat acomplex multiple fracture therefore requires an enormous mental efforton the part of the orthopedist since he or she cannot verify theallocation of the various fracture surfaces and thus bone fragments toone another at the picture screen. “Fast Visualization, Manipulation,and Analysis of Binary Volumetric Objects”, IEEE Computer Graphics andApplications, November 1991, pages 53-62, proposes a method forsplitting an anatomical structure into two components along a plane tobe arbitrarily defined. The separated components can be repositioned inspace independently of the original structure.

[0006] In “Simulating Motion of Anatomical Objects with Volume-Based3D-Visualization”, R. A.Robb (Editor): Visualization in BiomedicalComputing, Proc. SPIE 2359, 1994, pages 291-300, B. Plesser, U. Thiedeand K. H. Hohne propose the division of an anatomical subject intopartial subjects that can be subsequently converted into a new spatialarrangement.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide a method andan apparatus for separating an anatomical structure into its individualsubjects, so that these can be arbitrarily re-arranged independentlyfrom one another in the spatial presentation either individually and/orin groups.

[0008] This object is achieved in a method, an apparatus and a softwareproduct for imaging processing of datasets with a three-dimensionalcharacter that are obtained from medical examination procedures, whereina separation of the data of relevant anatomical structure as well asother structures is undertaken proceeding from data in the form ofvolume elements and a spatial presentation of at least one structure ofinterest is undertaken, and wherein at least one of the individualsubjects of the structure of interest is separated such that theindividual subject can be re-positioned in the spatial presentation. Asegmenting or separation of the individual subjects from one anotherensues by dividing the overall volume of the anatomical structure intopartial volumes in a first step, with an individual subject beingcompletely contained in the partial volume allocated to it. All otherdata not to be considered as belonging to this individual subject areremoved from this partial volume in a second step. The resultant data ofeach partial volume processed in this way are stored in a third step.

[0009] Time-consuming procedures thus can be shifted from the operationinto the planning phase. The precise planning of an intervention in thepreparatory phase of the operation not only shortens the duration of theintervention and, thus, produces less stress on the patient, but alsoenables more precise and safer work for the medical practitioner duringthe operation. Also advantageously, the use of suitable aids such as,for example, screws, nails, etc., can already be tested before theoperation. Likewise advantageously, implants can now be pre-shapedaccording to the identifiable conditions on the basis of the presentinvention and no longer need be intuitively designed during the courseof the operation.

[0010] In an embodiment of the invention, the partial volumes have theshape of a cuboid, as a result of which the individual volumes can beeasily joined. Together with the data of each partial volume, theappertaining coordinate information are also stored. The editing of 3Dcomputer tomography datasets is particularly advantageous, so theselection of a bone structure as a structure of interest, with theindividual bones and/or bone fragments as individual subjects of thestructure to be segmented, is especially advantageous.

DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a schematic 3D illustration of the osseous structure ofa wrist joint with a fracture and dislocation of the os metacarpal V,formed from a 3D computed tomography (CT) dataset.

[0012]FIG. 2 is an empirically produced partial volume from thedislocated bone fragment in FIG. 1.

[0013]FIG. 3 shows the dislocated bone fragment in FIGS. 1 and 2 alignedrelative to the second fragment of the os metacarpal V so that thefracture surfaces are parallel to and opposite from each other.

[0014]FIG. 4 shows the osseous structure of FIG. 1 with the bonefragments virtually joined in the image at the fracture surfaces.

[0015]FIG. 5 is a block diagram of the apparatus of the invention whichalso illustrates the method of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016]FIG. 1 provides a conceptualization of the graphic representationof a computer-tomographic 3D dataset as is currently available to asurgeon. In practice, the data are visualized by means of a methodreferred to as volume rendering, wherein the surface of the identifiedosseous structure is presented with a suitably calculated distributionof light and shadow so that it conveys a plastic impression of theunderlying spatial structure to the viewer or the surgeon.

[0017] A bone fracture with a dislocated fragment of the os metacarpal Vcan be clearly recognized in the left half of FIG. 1. The relativeposition of this bone fragment with respect to the other subjects of thegraphically visualized structure cannot be modified at this initialstage S0 of the inventive method since the structure for a single,interconnected subject in this stage as established by the standardmethods of medical image processing. Although a viewer has thepossibility of examining details such as, for example, fracture surfacesin greater detail by selecting a suitable angle of view, inspecting thetwo fracture surfaces for a form-fit requires an ability of the viewerto conceptualize that cannot always be assumed.

[0018] An assessment as to whether the two fracture surfaces can beseamlessly joined to one another assumes that the two fragments of thebroken bone can be aligned and positioned independently of one another.After segmentation of the dataset into anatomical structures, however,the illustrated bone structure is obtained as an interconnected subject.The subdivision into the discrete subjects of the structure that isunconsciously performed by the viewer, into bones and bone fragments inthe present example, is not reduplicated by the conventionally availablesegmenting methods.

[0019] In order to achieve a further segmenting of the structures withinan anatomical structure, the existing 3D CT dataset is first resolvedinto separate volumes according to method step S1 in FIG. 5, each ofthese volumes completely containing a complete sub-structure or adiscrete subject. In the aforementioned example, thus, such a partialvolume comprises an individual bone or an individual bone fragment. Tothat end, each discrete subject identified in the 3D CT dataset isadvantageously circumscribed by a cuboid in conformity with its spatialexpanse.

[0020] Many individual subjects are in immediate proximity to oneanother, for which reason component parts of neighboring subjects arealso generally contained in the individual partial volumes in additionto the desired individual subject. In the next step S2, the partialvolumes are therefore cleaned in that the data of the neighboringsubjects are eradicated in each of the partial volumes until thedescribed partial volume ultimately contains only the individual subjectallocated to it, the dislocated bone fragment in the example of FIG. 2.Advantageously, the data partial volumes produced in this way are storedtogether with the coordinate information allocated to them.

[0021] This advanced segmenting is implemented for all bones or,respectively, bone fragments of the 3D CT dataset S21, S22 and S23 sothat the original dataset can be presented from the sum of the datapartial volumes that are generated. The visual presentation of this sumS3 is initially the same as before the beginning of the segmentation ofthe anatomical structure into its isolatable subjects.

[0022] However, the fixed geometrical reference of the discrete subjectsrelative to one another has been eliminated at this point in the method.

[0023] As can be seen in the result thereof, for example in FIG. 3, theindividual subjects can now be individually selected and newly aligned.In this presentation, the dislocated bone fragment is aligned such thatthe two fracture surfaces reside parallel opposite one another. Comparedto this illustration, the bone fragment was displaced farther in FIG. 4,so that the two fracture surfaces have been brought into coincidence. Itis only the inventive segmenting of the original 3D CT dataset thatmakes this virtual repositioning of bone fragments possible.

[0024]FIG. 5 outlines the implementation of the described method in anapparatus 50 for medical image processing. The 3D dataset supplied bythe medical analysis device in an examination is transmitted to theapparatus 50. The transmission can ensue arbitrarily, for example withthe assistance of a data carrier or via a data bus or, respectively, anetwork. The further-processing of the dataset with the processingdevice 55 ensues according to method steps S0 through S3. Proceedingfrom the anatomical structure S0 that has already been segmented, thevolume covering this structure is divided into a plurality of partialvolumes in the first method step S1, whereby each partial volumecompletely envelopes a discrete subject of the structure of interest.The cleaning S2 ensues for all partial volumes S1 and S2 in that alldata not belonging to the discrete subject of a partial volume areeradicated therefrom S23. Finally, all partial volumes and, thus, alldiscrete subjects of the anatomical structure of interest are displayedS3 on the display device 53. The operator can influence the presentationvia commands or control signals that are given to the processing devicevia an input device. The memory device 52 accepts the original datasetsand the data that arise during the course and as a result of thedescribed image processing process.

[0025] Although modifications and changes may be suggested by thoseskilled in the art, it is the invention of the inventor to embody withinthe patent warranted heron all changes and modifications as reasonablyand properly come within the scope of his contribution to the art.

1. Method for imaging processing of datasets with a three-dimensionalcharacter that are obtained from medical examination procedures, wherebya separation of the data of relevant anatomical structure as well asother structures is undertaken proceeding from data in the form ofvolume elements and a spatial presentation of at least one structure ofinterest is undertaken, characterized in that at least one of theindividual subjects of the structure of interest is separated such thatthe individual subject can be re-positioned in the spatial presentation.2. Method for imaging processing of datasets with a three-dimensionalcharacter that are obtained from medical examination proceduresaccording to claim 1, characterized in that the separation of theindividual subjects from one another ensues according to the followingsteps: every individual subject has a partial volume allocated to itsuch that the individual subject is completely contained therein; andall data within this partial volume that are not to be counted asbelonging to this individual subject are removed; and the data of eachand every partial volume generated in this way are stored.
 3. Method forimaging processing of datasets with a three-dimensional character thatare obtained from medical examination procedures according to claim 2,characterized in that the partial volume comprises the shape of acuboid.
 4. Method for imaging processing of datasets with athree-dimensional character that are obtained from medical examinationprocedures according to claim 2 or 3, characterized in that the data ofthe partial volume are stored together with the appertaining coordinateinformation.
 5. Method for imaging processing of datasets with athree-dimensional character that are obtained from medical examinationprocedures according to one of the claims 1 through 4, characterized inthat the datasets acquired from medical examination procedures are 3Dcomputer tomography datasets.
 6. Method for imaging processing ofdatasets with a three-dimensional character that are obtained frommedical examination procedures according to one of the claims 1 through5, characterized in that the structure of interest is an osseousstructure and the individual subjects of the structure are bones and/orbone fragments.
 7. Apparatus (50) for imaging processing of datasets(51) with a three-dimensional character acquired from medicalexamination procedures, comprising a memory device (52) for storing atleast one dataset that is based on a spatial presentation of relevantanatomical structures and/or partial structures, and a graphic displaydevice (53) for the visual presentation of at least one structure ofinterest on which the dataset is based, and an input device (54) forinputting commands, and a processing device (55) for processing theinput commands, for the control of the spatial presentation of datasetsrepresenting graphic subjects and for editing these datasets,characterized in that the processing device separates at least one ofthe individual subjects of the structure of interest from the structureof interest such that the individual subject can be repositioned in thespatial presentation.
 8. Apparatus for imaging processing of datasetswith a three-dimensional character acquired from medical examinationprocedures according to claim 7, characterized in that the processingdevice undertakes the separation of the individual subjects from oneanother in that it first allocates a partial volume to each and everyindividual subject such that the individual subject is completelycontained therein, and subsequently removes all data in the partialvolume that cannot be counting as belonging to the allocated individualsubject, and, last, stores the data of each and every partial volumegenerated in this way in the memory device.
 9. Apparatus for imagingprocessing of datasets with a three-dimensional character acquired frommedical examination procedures according to claim 8, characterized inthat the processing device employs a cuboid as shape of the partialvolume.
 10. Apparatus for imaging processing of datasets with athree-dimensional character acquired from medical examination proceduresaccording to claim 8 or 9, characterized in that the processing devicestores the data of the partial volume in the memory device together withthe appertaining coordinate information.
 10. Method for imagingprocessing of datasets with a three-dimensional character that areobtained from medical examination procedures according to claim 8 or 9,characterized in that the processing device stores the data of thepartial volume in the memory device together with the appertainingcoordinate information.
 11. Apparatus for imaging processing of datasetswith a three-dimensional character acquired from medical examinationprocedures according to one of the claims 7 through 7, characterized inthat the datasets acquired from medical examination procedures are 3Dcomputer tomography datasets.
 12. Apparatus for imaging processing ofdatasets with a three-dimensional character acquired from medicalexamination procedures according to one of the claims 1 through 11,characterized in that the structure of interest is an osseous structureand the individual subjects of the structure are bones and/or bonefragments.
 13. Computer software product for imaging processing ofdatasets with a three-dimensional character acquired from medicalexamination procedures that, when executed on a computer, undertakes aseparation of the data into relevant anatomical structures as well asother structures proceeding from data in the form of volume elements andspatially presents at least one structure of interest, characterized inthat it implements a separation of at least one of the individualsubjects of the structure of interest from the structure of interestsuch that the individual subject can be repositioned in the spatialpresentation.
 14. Computer software product for imaging processing ofdatasets with a three-dimensional character acquired from medicalexamination procedures according to claim 13, characterized in that itundertakes the separation of the individual subjects from one another inthat it allocates a partial volume to each individual subject in a firststep such that the individual subject is completely contained therein,and, in a second step, removes all data within this partial volume thatcannot be counted as belonging to this individual subject, and in athird step, saves the data of each partial volume so generated. 15.Computer software product for imaging processing of datasets with athree-dimensional character acquired from medical examination proceduresaccording to claim 14, characterized in that it utilizes a cuboid as ashape of the partial volume.
 16. Computer software product for imagingprocessing of datasets with a three-dimensional character acquired frommedical examination procedures according to claim 14 or 15,characterized in that it saves the data of the partial volume togetherwith the coordinate information pertaining thereto.
 17. Computersoftware product for imaging processing of datasets with athree-dimensional character acquired from medical examination proceduresaccording to any of the claims 13 through 16, characterized in that thedatasets acquired from medical examination procedures are 3D computertomography datasets.
 18. Computer software product for imagingprocessing of datasets with a three-dimensional character acquired frommedical examination procedures according to any of the claims 13 through17, characterized in that the structure of interest is a osseousstructure, and the individual objects of the structure are bones and/orbone fragments.